Functional performance of the knee after intraarticular anesthesia

Motor imagery in high-functioning individuals with chronic anterior cruciate ligament deficiency: A cross-sectional study

BACKGROUND

There is increasing evidence that motor imagery performance (MIP) is impaired in conditions that have a component of movement dysfunction. However, MIP has not been investigated in people with chronic anterior cruciate ligament (ACL) deficiency who experience limited disability and function at high levels.

HYPOTHESIS

This study had three objectives: (1) to assess implicit MIP in individuals with a chronic ACL deficient (ACLD) knee compared with healthy controls (i.e., intact anterior cruciate ligament); (2) to determine if the location of ACL deficiency affects MIP (dominant versus non-dominant leg); and (3) to determine if impairment in MIP is specific to the side (injured versus non-injured) of ACL deficiency.

METHODS

Forty-five participants with chronic ACLD knee and 44 healthy controls completed a left/right judgement task of pictured knees using the "Recognise" app to evaluate implicit MIP. Accuracy and reaction time of judgements were compared between groups. Additionally, within the chronic ACLD knee group, we made comparisons between the dominant ACLD knee and non-dominant ACLD knee subgroups and between the injured knee and the non-injured knee of the ACLD group.

RESULTS

There were no differences in implicit MIP between the ACLD knee and the control group, the non-injured knee versus injured knee of the ACLD knee group, or the dominant ACLD knee versus non-dominant ACLD knee subgroups.

CONCLUSION

Implicit MIP is not disrupted in high functioning individuals with chronic ACLD knee.

Patellar movement perception related to a backward-leaning standing position

[Purpose] To investigate the patellar movement perception related to backward-leaning standing. [Subjects and Methods] Both the patellar range of motion during backward-leaning standing and perception related to patellar movement were analyzed using television-x irradiation images in 12 randomly selected healthy young individuals. [Results] Starting in a relaxed condition, two types of patellar movements were confirmed: those where the patella moves (patellar movement trials) and those where the patella does not move (patellar non-movement trials) during backward-leaning standing. The rate of the perceived patellar motion in the patellar movement trials was significantly higher (90.9%) than that in the patellar non-movement trials (66.7%). When starting in a quadriceps-contracted condition, the rate of perceived trials (77.0%) was significantly lower than that of the trials started in a relaxed condition. [Conclusion] The perception of patellar movement while backward-leaning standing may contribute to the perception of a backward standing position especially when the patella really moves.

Assessing proprioception: A critical review of methods

To control movement, the brain has to integrate proprioceptive information from a variety of mechanoreceptors. The role of proprioception in daily activities, exercise, and sports has been extensively investigated, using different techniques, yet the proprioceptive mechanisms underlying human movement control are still unclear. In the current work we have reviewed understanding of proprioception and the three testing methods: threshold to detection of passive motion, joint position reproduction, and active movement extent discrimination, all of which have been used for assessing proprioception. The origin of the methods, the different testing apparatus, and the procedures and protocols used in each approach are compared and discussed. Recommendations are made for choosing an appropriate technique when assessing proprioceptive mechanisms in different contexts.

The effects of cryotherapy on proprioception system

Proprioception plays an important role in the complex mechanism of joint control. Contemporary sport activities impose extremely high physical demands on athletes. Winter sports are played in areas with excessively low temperatures. Moreover, many athletes are subjected to treatments that involve local lowering of the body temperature before, during, and after physical activity. This work reviews the current knowledge regarding the influence of local cryotherapy on the proprioception system. The reviewed literature identified several tests that evaluate different aspects of proprioception. There is no universally agreed protocol, or clear set of criteria for test conditions. The outcomes of different tests and assessments of cryotherapy procedures using different cold modalities are poorly correlated. In general, the published results on the mechanism of cryotherapy effects on proprioception are not uniquely conclusive and are frequently contradictory. Additional high-quality research is required to explicitly answer the following questions: (1) whether local cryotherapy influences all aspects of proprioception; (2) whether the current methods of evaluation are adequate for the exploration of the relationship between cryotherapy and proprioception; and (3) whether the application of local cryotherapy is safe for athletes regarding proprioception. The review clearly showed that there is no comprehensive model relating cryotherapy and proprioception.

The representation of egocentric space in the posterior parietal cortex

The posterior parietal cortex (PPC) is the most likely site where egocentric spatial relationships are represented in the brain. PPC cells receive visual, auditory, somaesthetic, and vestibular sensory inputs; oculomotor, head, limb, and body motor signals; and strong motivational projections from the limbic system. Their discharge increases not only when an animal moves towards a sensory target, but also when it directs its attention to it. PPC lesions have the opposite effect: sensory inattention and neglect. The PPC does not seem to contain a "map" of the location of objects in space but a distributed neural network for transforming one set of sensory vectors into other sensory reference frames or into various motor coordinate systems. Which set of transformation rules is used probably depends on attention, which selectively enhances the synapses needed for making a particular sensory comparison or aiming a particular movement.

Research Advancements in Humanoid Compression Garments in Sports

The utilization of sport-related compression garments has attracted a great deal of attention from among Sports Science scholars. The function of the garments, such as to maintain muscle functions, reduce sports injuries and improve athletic performance, has been an issue of debate since the beginning of the new century. In this study, a number of methods including a literature review, logical analysis and mathematical statistics, are used to analyse earlier compression garments research, which can be found by searching hardcopy journals and online databases. Among the existing studies, most have tested and confirmed the functions of the garments; however, only a few have mentioned the underlying mechanism. Thus, by using more advanced and appropriate compression materials, future studies into compression garments will be focused on the vibration characteristics of muscles (soft tissues), and especially on their proprioceptive sensation, neuromuscular control, injury prevention and performance enhancement.

Alterations in in vivo knee joint kinematics following a femoral nerve branch block of the vastus medialis: Implications for patellofemoral pain syndrome

BACKGROUND

A potential source of patellofemoral pain, one of the most common problems of the knee, is believed to be altered patellofemoral kinematics due to a force imbalance around the knee. Although no definitive etiology for this imbalance has been found, a weak vastus medialis is considered a primary factor. Therefore, this study's purpose was to determine how the loss of vastus medialis obliquus force alters three-dimensional in vivo knee joint kinematics during a volitional extension task.

METHODS

Eighteen asymptomatic female subjects with no history of knee pain or pathology participated in this IRB approved study. Patellofemoral and tibiofemoral kinematics were derived from velocity data acquired using dynamic cine-phase contrast MRI. The same kinematics were then acquired immediately after administering a motor branch block to the vastus medialis obliquus using 3-5ml of 1% lidocaine. A repeated measures analysis of variance was used to test the null hypothesis that the post- and pre-injection kinematics were no different.

FINDINGS

The null hypothesis was rejected for patellofemoral lateral shift (P=0.003, max change=1.8mm, standard deviation=1.7mm), tibiofemoral lateral shift (P<0.001, max change=2.1mm, standard deviation=2.9mm), and tibiofemoral external rotation (P<0.001, max change=3.7°, standard deviation=4.4°).

INTERPRETATION

The loss of vastus medialis obliquus function produced kinematic changes that mirrored the axial plane kinematics seen in individuals with patellofemoral pain, but could not account for the full extent of these changes. Thus, vastus medialis weakness is likely a major factor in, but not the sole source of, altered patellofemoral kinematics in such individuals.

Does the nervous system depend on kinesthetic information to control natural limb movements?

This target article draws together two groups of experimental studies on the control of human movement through peripheral feedback and centrally generated signals of motor commands. First, during natural movement, feedback from muscle, joint, and cutaneous afferents changes; in human subjects these changes have reflex and kinesthetic consequences. Recent psychophysical and microneurographic evidence suggests that joint and even cutaneous afferents may have a proprioceptive role. Second, the role of centrally generated motor commands in the control of normal movements and movements following acute and chronic deafferentation is reviewed. There is increasing evidence that subjects can perceive their motor commands under various conditions, but that this is inadequate for normal movement; deficits in motor performance arise when the reliance on proprioceptive feedback is abolished either experimentally or because of pathology. During natural movement, the CNS appears to have access to functionally useful input from a range of peripheral receptors as well as from internally generated command signals. The unanswered questions that remain suggest a number of avenues for further research.

Implications of neural networks for how we think about brain function

Engineers use neural networks to control systems too complex for conventional engineering solutions. To examine the behavior of individual hidden units would defeat the purpose of this approach because it would be largely uninterpretable. Yet neurophysiologists spend their careers doing just that! Hidden units contain bits and scraps of signals that yield only arcane hints about network function and no information about how its individual units process signals. Most literature on single-unit recordings attests to this grim fact. On the other hand, knowing a system's function and describing it with elegant mathematics tell one very little about what to expect of interneuronal behavior. Examples of simple networks based on neurophysiology are taken from the oculomotor literature to suggest how single-unit interpretability might decrease with increasing task complexity. It is argued that trying to explain how any real neural network works on a cell-by-cell, reductionist basis is futile and we may have to be content with trying to understand the brain at higher levels of organization.

An investigation into the effects of a simulated effusion in healthy subjects on knee kinematics during jogging and running

BACKGROUND

Knee joint effusion can lead to changes in the activation of surrounding musculature and result in delayed return to baseline daily and sporting activity following injury. However, the effects of an isolated knee joint effusion on control of movement during cyclical activities such as gait are poorly understood.

METHODS

Knee angular displacement and velocity was measured during treadmill jogging (8 km h(-1)) and running (12 km h(-1)) in 12 healthy subjects before and after a simulated knee joint effusion. Two separate pre-effusion recordings were taken to account for test-retest variability in gait measurement techniques.

FINDINGS

Subjects demonstrated a small yet significant decrease in peak knee flexion following heel strike at 8 km h(-1) as a result of the effusion (P<0.05). However, there were no significant effects seen at 12 km h(-1).

INTERPRETATION

Previous work has suggested that knee joint movement during walking and jump landing is affected by an effusion. However, this work demonstrates that these effects are minimal during jogging and running. Our results suggest that it may be prudent to consider measurement variability in future studies of this nature.

Head and neck position sense

Traumatic minor cervical strains are common place in high-impact sports (e.g. tackling) and premature degenerative changes have been documented in sports people exposed to recurrent impact trauma (e.g. scrummaging in rugby) or repetitive forces (e.g. Formula 1 racing drivers, jockeys). While proprioceptive exercises have been an integral part of rehabilitation of injuries in the lower limb, they have not featured as prominently in the treatment of cervical injuries. However, head and neck position sense (HNPS) testing and re-training may have relevance in the management of minor sports-related neck injuries, and play a role in reducing the incidence of ongoing pain and problems with function. For efficacious programmes to be developed and tested, fundamental principles associated with proprioception in the cervical spine should be considered. Hence, this article highlights the importance of anatomical structures in the cervical spine responsible for position sense, and how their interaction with the CNS affects our ability to plan and execute effective purposeful movements. This article includes a review of studies examining position sense in subjects with and without pathology and describes the effects of rehabilitation programmes that have sought to improve position sense. In respect to the receptors providing proprioceptive information for the CNS, the high densities and complex arrays of spindles found in cervical muscles suggest that these receptors play a key role. There is some evidence suggesting that ensemble encoding of discharge patterns from muscle spindles is relayed to the CNS and that a pattern recognition system is used to establish joint position and movement. Sensory information from neck proprioceptive receptors is processed in tandem with information from the vestibular system. There are extensive anatomical connections between neck proprioceptive inputs and vestibular inputs. If positional information from the vestibular system is inaccurate or fails to be appropriately integrated in the CNS, errors in head position may occur, resulting in an inaccurate reference for HNPS, and conversely if neck proprioceptive information is inaccurate, then control of head position may be affected. The cerebellum and cortex also play a role in control of head position, providing feed-forward and modulatory influences depending on the task requirements. Position-matching tasks have been the most popular means of testing position sense in the cervical spine. These allow the appreciation of absolute, constant and variable errors in positioning and have been shown to be reliable. The results of such tests indicate that errors are relatively low (2-5 degrees). It is apparent that error is not consistently affected by age, a finding similar to studies undertaken in peripheral joints. Furthermore, the range of motion in which subjects are tested does not consistently affect accuracy in a predictable manner. However, it is evident that impairments in position sense are observed in individuals who have experienced whiplash-type injuries and individuals with chronic head and neck pain of non-traumatic origin (e.g. cervical spondylosis). While researchers advocate comprehensive retraining protocols, which include eye and neck motion targeting tasks and coordination exercises, as well as co-contraction exercises to reduce such impairments, some studies show that more general exercises and manipulation may be of benefit. Overall, there is limited information concerning the efficacy of treatment programmes.

Intra-articular anesthesia and knee muscle response

BACKGROUND

Many receptors located within the intra-articular knee structures contribute to the neuromuscular responses of the knee. The purpose was to compare the automatic postural response induced by a perturbation at the foot before and after an intra-articular injection of a local anesthetic (bupivicaine), after a saline (sham) injection, and after no intra-articular injection (control) in the knee.

METHODS

Muscle onset latencies and automatic response magnitudes for the vastus medialis, vastus lateralis, biceps femoris, medial hamstrings, tibialis anterior, and gastrocnemius were measured using electromyography (EMG) when anteriorly directed perturbations were applied to the feet of 30 subjects. All subjects then received a lidocaine skin injection followed by: an intra-articular bupivicaine injection (treatment group); an intra-articular saline injection (sham group); or no injection (control group), depending on their randomized group assignment. The perturbation tests were then repeated.

FINDINGS

Muscle onset latencies and automatic response magnitudes did not change as a result of the intra-articular injections. Latencies were significantly greater for the vastus medialis and vastus lateralis when compared to the medial hamstrings, biceps femoris and tibialis anterior (P<0.001). Automatic response magnitudes for the tibialis anterior were significantly greater than those of the hamstrings, which were greater than those of the quadriceps (P<0.001).

INTERPRETATION

There were no differences in muscle response when anteriorly directed perturbations were applied to the foot with or without an injection of local anesthetic in the knee. Intra-articular receptors were either unaffected by the anesthetic or the extra-articular receptors or receptors of the other joints were able to compensate for their loss.

Movement discrimination after intra-articular local anaesthetic of the ankle joint

BACKGROUND

The effect on clinical safety of dampening articular mechanoreceptor feedback at the ankle is unknown. Injection of the ankle joint for pain control may result in such dampening. Athletes receiving intra-articular local anaesthetic may therefore be at increased risk of sustaining ankle injuries, which are a common reason for missed sporting participation.

OBJECTIVE

To determine the effect of intra-articular local anaesthetic on movement discrimination at the ankle joint.

DESIGN

Prospective, randomised, double-blinded, placebo-controlled, cross-over trial.

SETTING

Australian Institute of Sport Medical Centre, Canberra, Australia.

PATIENTS

Twenty two healthy subjects (44 ankles) aged 18-26 were recruited for the three visits of the study.

INTERVENTIONS

Subjects were tested for their initial movement discrimination scores using the active movement extent discrimination apparatus (AMEDA). They then received ultrasound-guided intra-articular injections of local anaesthetic (2% lignocaine hydrochloride) or normal saline, on two separate later occasions, before further AMEDA assessment.

MAIN OUTCOME MEASURES

Change in movement discrimination scores after intra-articular injection of local anaesthetic or saline.

RESULTS

Movement discrimination scores were not significantly different from control ankles after injection of either local anaesthetic or saline into the ankle joint.

CONCLUSIONS

The intra-articular injection of neither 2 ml lignocaine nor an equivalent amount of normal saline resulted in significant effects on movement discrimination at the ankle joint. These results suggest that injections of local anaesthetic into the ankle joint are unlikely to significantly affect proprioception and thereby increase injury risk.

Proprioception in Individuals with ACL-Deficient Knee and Good Muscular and Functional Performance

The objective of this study was to verify whether proprioception is affected in individuals with ACL-deficient knees and good functional and muscular performances. Eleven subjects with ACL injury and 11 controls participated in the study. Functional performance was assessed using the Cincinnati Knee Rating System (CKRS), hop index, and figure-eight ratio. An isokinetic test was done to evaluate muscular performance. Proprioception was evaluated through position, sense and threshold tests. Analyses of variance were used for data analysis. The injured subjects scored significantly lower in the CKRS (p = 0.001). No statistically significant differences were found in the hop index, in the figure-eight ratio, or in peak torque. There were no statistically significant differences in proprioception bettween groups and between legs. These results indicated that the individuals evaluated in this study with ACL injury and good functional and muscular performance did not have proprioceptive deficits, suggesting that the ligament mechanoreceptors, in some cases, might not contribute relevantly to proprioception.

The effect of degenerative arthritis and prosthetic arthroplasty on shoulder proprioception

The effect of glenohumeral arthritis and subsequent total shoulder arthroplasty (TSA) on shoulder proprioception has not been evaluated previously. A prospective analysis of 20 consecutive patients with unilateral advanced glenohumeral arthritis who underwent TSA was undertaken. Shoulder proprioception testing for passive position sense and detection of motion was performed 1 week before surgery and 6 months after TSA. The presence of glenohumeral arthritis had a significant effect on position sense for all 3 planes tested (flexion, abduction, and external rotation). There were significant differences (P < .05) compared with the uninvolved shoulder and with a group of 20 age- and gender-matched subjects without a history of shoulder problems. Six months after TSA, position sense was significantly improved (P < .05) and was not significantly different from that in the contralateral shoulder or the comparison group. Detection of motion was also significantly worse in the arthritic group compared with that in the uninvolved contralateral side (P < .05). Six months after TSA, the sensitivity to detection of motion improved (P < .01) and was not significantly different than that in the uninvolved contralateral shoulder. In addition, the postoperative values for the involved shoulder were not significantly different than those in the age- and gender-matched comparison group. This study demonstrates a significant decrease in proprioceptive function in patients with advanced glenohumeral arthritis. After TSA, there was a marked improvement in proprioception.

Strain on the Anterior Cruciate Ligament during Closed Kinetic Chain Exercises

PURPOSE

The purpose of this investigation was to characterize the ACL strains produced during four commonly prescribed CKC exercises; the step-up, the step-down, the lunge, and the one-legged sit to stand. We hypothesized that the ACL strains produced during the lunge and one-legged sit to stand exercises (the exercises that challenge the leg musculature to a greater extent and utilize greater hip flexion) would be less than those produced during the step-up and step-down exercises.

METHODS

The strains in the anteromedial bundle of the ACL were measured while nine subjects, who had normal ligaments, performed the four exercises. Peak ACL strain values and the ACL strain patterns as a function of knee flexion angle were compared between exercises.

RESULTS

No significant differences were found between the peak ACL strain values (mean +/- SEM) between exercises (step-up: 2.5 +/- 0.36; step-down: 2.6 +/- 0.34; lunge 1.9 +/- 0.50; one-legged sit to stand: 2.8 +/- 0.27). The mean ACL strain values as a function of knee flexion angle were not significantly different. On average, there was a significant increase in ACL strain as the knee was extended for each exercise.

CONCLUSIONS

The ACL strain responses produced during these CKC exercises were equal and similar to those produced during other rehabilitation exercises (i.e., squatting, active extension of the knee) previously tested.

Analyses of dynamic co-contraction level in individuals with anterior cruciate ligament injury

BACKGROUND

A complete understanding of neural mechanisms by which ligament receptors may contribute to joint stability is not well established. It has been suggested that these receptors may be involved in a neuromuscular process related to the modulation of dynamic co-contraction, as a means of guaranteeing functional joint stability.

HYPOTHESIS

Individuals with ACL injury have diminished dynamic co-contraction.

STUDY DESIGN

Exploratory, cross-sectional design.

METHODS

Ten subjects with unilateral ACL injury treated conservatively, and ten subjects without history of injury participated in the study. The co-contraction level was assessed through EMG recordings of the vastus lateralis and biceps femoris before and after a perturbation imposed on the subjects during a walking task.

RESULTS

Subjects with ACL injury presented significantly lower co-contraction level pre-perturbation (p = 0.045) and post-perturbation (p = 0.046) than those in the control group.

CONCLUSIONS

The bilateral decrease in muscular co-contraction presented by individuals with ACL injury suggests that ligament and joint receptors may be responsible for a bilateral dynamic increase in muscle and joint stiffness that could result in a greater joint stability.

CLINICAL RELEVANCE

This study analyzed a neuromuscular mechanism that might contribute to the functional stability of the knee joint.

The effect of local and general fatigue on knee proprioception

PURPOSE

The purpose of this study was to compare the effects of local and general fatigue loads on knee proprioception.

TYPE OF STUDY

Experimental controlled study.

METHODS

Proprioception of the knee joint was evaluated by measuring absolute angular error (AAE) at matching defined index angles before and after 2 different types of fatigue protocols (local load and general load) in 27 healthy male volunteers. Local load was provided with maximum isokinetic knee flexion-extension on the isokinetic dynamometer, and general load was 5 minutes running on a treadmill.

RESULTS

After local load, a significant decrease in peak torque of knee flexors and extensors was found, but no significant change in AAE was seen. In contrast, after general load, a significant increase of AAE was noted without significant muscle weakness.

CONCLUSIONS

The different results in previous studies evaluating the effect of fatigue on knee proprioception may have been affected by the difference of fatigue protocols, whether local or general load. Although local load was intended to produce local fatigue of the knee, which may cause dysfunction of muscle mechanoreceptors, general load may have produced general fatigue and affected other mechanisms in the proprioceptional pathway. The results of the present study suggest that decreased reproduction ability after general load is not due to the loss of peripheral afferent signals, but to other factors, especially deficiency of central processing of proprioceptive signals.

CLINICAL RELEVANCE

To prevent knee injury caused by fatigue-induced proprioceptional decline, muscle endurance training alone is not enough, and neuromuscular training, including central motor programming, is essential.

The effects of compressive load and knee joint torque on peak anterior cruciate ligament strains

BACKGROUND

High graft strains incurred during rehabilitation after anterior cruciate ligament reconstruction may be minimized if an external compressive load is simultaneously applied to the joint during closed kinetic chain exercises.

HYPOTHESES

Peak anterior cruciate ligament strains will 1). increase with an increase in resistance torque during an exercise that involves concentric contraction of the extensor mechanism, 2). decrease with an increase in resistance torque during an exercise that involves concentric contraction of the flexors, and 3). decrease when an external compressive load is applied to the knee during both exercises relative to the no external compressive load condition.

STUDY DESIGN

Controlled laboratory study.

METHODS

Strains in the anteromedial bundle were measured in 10 subjects with normal ligaments. Flexor and extensor exercises were performed against controlled resistance torques with and without a compressive load applied to the foot.

RESULTS

An increase in resistance produced an increase in peak anterior cruciate ligament strain for the extensor exercise with no compressive load applied. During the flexor exercise without a compressive load, an increase in resistance produced a decrease in peak strains. During the extensor exercise, the peak anterior cruciate ligament strain was not reduced with the application of the external compressive force.

CONCLUSIONS

Extensor and flexor exercises that incorporate an external compressive load do not shield the anterior cruciate ligament from strain. However, no additional increase in strain occurs with an increase in resistance when the external compressive load is applied. Thus, it may be possible to increase the activity of the quadriceps muscles without increasing the strain by applying a compressive load (as with closed kinetic chain exercises).

Perceptibility of large and sequential changes in somatosensory information during leaning forward and backward when standing

11 healthy young men served as subjects in two experiments on perceptibility of (1) large changes in foot pressure and muscle activity induced by body leaning and (2) sequential changes in pressure at the first toe and the head of the first metatarsalis when leaning forward. The effects of reduced sensitivity on that perceptibility were also studied by repeating the experiments while cooling localized plantar areas of the sole (the head of the first metatarsalis, the first toe, and the heel). Under the normal (noncooled) condition, all subjects accurately perceived maximum pressure at the head of the first metatarsalis, but most subjects misperceived the second large increase in pressure at the first toe and in muscle activity as the first large increase. Under the cooling condition, localized cooling did not affect the perceptibility of maximum pressure at the head of the first metatarsalis or the activity in the tibialis anterior, but the perceptibility of pressure at the first toe and activity of the abductor hallucis were reduced. There were individual differences in perceptibility of activity of the rectus femoris when the heel was cooled. Perceptibility of sequential changes in the pressure was affected differently by the localized cooling of each region. Given these findings, we discussed the role and interrelatedness of pressure sensation in perceiving large and sequential changes in somatosensory information while standing and leaning forward and backward.

Review of knee proprioception and the relation to extremity function after an anterior cruciate ligament rupture

Several tests of human conscious knee proprioception have been described, but there is no consensus or reference standard established. Difficulties remain in the separation of information originating from muscles, tendons, and joints, and the tests cannot discriminate between loss of afferent signals or altered activity in the remaining receptors. There is convincing evidence from several descriptive studies that the afferent information is altered after a knee ligament injury and severely disturbed in some patients with anterior cruciate ligament (ACL) injuries. However, an inherent inferior proprioceptive ability may also exist in some individuals, which makes them vulnerable to injuries. The deficits in proprioception have mostly been studied and related to the consciously registered sense, whereas the extent of possible disturbances of the unconscious or reflectory mechanisms is largely unknown. The latter may, at least from a theoretical point of view, be predominantly contributing to the overall afferent regulation, and a possibility for major defects thus exists, since there is no knowledge of the quantified relation between the conscious and unconscious part. The clinical importance of the altered afferent information has not been evaluated properly, and the role of proprioception that contributes to function has yet to be investigated. A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals. Little is known about whether training can restore defects in sensory information or by which mechanisms possible compensatory pathways are established. In rehabilitation, each patient must, however, create muscle strength, alertness, and stiffness in harmony with the disturbed mechanics of the knee, which are present both after nonoperative treatment of the ACL and after a reconstruction of the ACL.

Functional instability of the ankle and the role of neuromuscular control: a comprehensive review

A review of current knowledge of the clinical syndrome of functional ankle instability is presented. Recent evidence has demonstrated that the majority of patients with functional instability of the ankle do not have mechanical hypermobility of the ankle joint. Functional instability of the ankle results from a loss of neuromuscular control. Components of neuromuscular control include proprioception, muscle strength, muscle reaction time, and postural control. Proprioceptive deficits lead to a delay in peroneal reaction time, which appears to be a peripheral reflex. Proprioception and eversion muscle strength improve with the use of passive supportive devices. Balance and postural control of the ankle appear to be diminished after a lateral ankle sprain and can be restored through training that is mediated through central nervous mechanisms. Methods of detecting deficits in neuromuscular control are presented along with rehabilitation techniques to treat functional instability of the ankle.

The effect of weightbearing and external loading on anterior cruciate ligament strain

A force balance between the ligaments, articular contact, muscles and body weight maintains knee joint stability. Thus, it is important to study anterior cruciate ligament (ACL) biomechanics, in vivo, under weightbearing conditions. Our objective was to compare the ACL strain response under weightbearing and non-weightbearing conditions and in combination with three externally applied loadings: (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varus-valgus moments. A strain transducer was implanted on the ACL of 11 subjects. All joint loadings were performed with the knee at 20 degrees of flexion. A significant increase in ACL strain was observed as the knee made the transition from non-weightbearing to weightbearing. During anterior shear loading, the strain values produced during weightbearing were greater than those of the non-weightbearing knee (shear loads <40N). At higher shear loads, the strain values became equal. During axial torsion, an internal torque of 10Nm strained the ACL when the knee was non-weightbearing while an equivalent external torque did not. Weightbearing significantly increased ACL strain values in comparison to non-weightbearing with the application of external torques and low internal torques (<3Nm). The strains became equal for higher internal torques. For V-V loading, the ACL was not strained in the non-weightbearing knee. However, weightbearing increased the ACL strain values over the range of moments tested. These data have important clinical ramifications in the development of rehabilitation protocols following ACL reconstruction since weightbearing has been previously thought to provide a protective mechanism to the healing graft.

Comparison of proprioception in arthritic and age-matched normal knees

BACKGROUND

Proprioception--one's ability to sense joint position and joint motion--is affected by factors such as age, muscle fatigue, and osteoarthritis. Most proprioception studies have focused on young active subjects or on recipients of total knee replacements. Few have involved a population with arthritic knees prior to total knee replacement or persons similar in age to patients with advanced knee arthritis who are to have total knee arthroplasty. The purpose of the present study was to determine (1) if proprioception in arthritic knees differs from proprioception in nonarthritic, age-matched, normal knees; (2) if, when proprioception in one knee is reduced by the presence of advanced gonarthrosis, it also is reduced in the contralateral knee irrespective of the presence of arthritis; and (3) if a person's grade of arthritis is associated with his or her level of proprioception.

METHODS

This study compared the proprioception levels of a group of 117 patients who were scheduled for total knee arthroplasty because of severe arthritis (mean age, 67.9 years) with those of a control group of forty patients who were recruited from a hospital-based cardiac rehabilitation program and did not have knee arthritis (mean age, 68.3 years). We used a customized Biodex System 2 Multi-Joint Testing and Rehabilitation System to compare proprioception (the threshold to detection of passive motion) between the two groups.

RESULTS

Middle-aged and elderly persons with advanced knee arthritis were significantly less able to detect passive motion of the knee than were middle-aged and elderly persons without knee arthritis. Patients who had arthritis in only one knee had a reduced ability to detect passive motion of both knees. There was no significant association between the radiographic severity of arthritis and the threshold to detection of passive motion in patients with advanced knee arthritis.

CONCLUSIONS

Knee proprioception in middle-aged and elderly persons with advanced knee arthritis is reduced in comparison with that in middle-aged and elderly persons without arthritis. Such loss of proprioception is independent of the severity of knee arthritis and may foretell the development of arthritis. When a patient has reduced proprioception with regard to one knee affected by arthritis, he or she also has reduced proprioception with regard to the contralateral knee, independent of the presence or severity of degenerative arthritis. When an investigator is evaluating changes in proprioception after knee arthroplasty, it is best to compare the knee with the patient's untreated knee rather than with age-matched controls.

The influence of functional knee bracing on the anterior cruciate ligament strain biomechanics in weightbearing and nonweightbearing knees

Functional knee braces are commonly prescribed after anterior cruciate ligament injury or reconstruction; however, their ability to protect the ligament, or graft, remains unclear. Our objective was to evaluate the anterior cruciate ligament strain response in braced and unbraced knees during weightbearing and nonweightbearing in combination with three externally applied loads: 1) anterior-posterior shear forces, 2) internal-external torques, and 3) varus-valgus moments. The Legend brace was tested. All external loads were applied to the tibia with the knee flexed to 20 degrees. Reproducible data were obtained from 11 subjects. For anterior shear loads up to 130 N, the brace significantly reduced strain values compared with the unbraced knee during nonweightbearing and weightbearing conditions. For internal torques of the tibia (up to 9 N x m), strain in the braced knee was significantly less than in the unbraced knee when the knee was nonweightbearing only. The brace did not reduce strain values when the knee was subjected to external torques (9 N x m) or varus-valgus moments (10 N x m) in weightbearing and nonweightbearing knees. These data indicate that a functional knee brace can protect the anterior cruciate ligament during anterior-posterior shear loading in the nonweightbearing and weightbearing knee and during internal torques in the nonweightbearing knee.

Influence of hysteresis on joint position sense in the human knee joint

During muscle lengthening in a movement cycle the firing rate of muscle spindles is higher than during shortening. This phenomenon, known as hysteresis, has implications for movement control. Therefore, it should have an impact on joint position sense (JPS), the subject's awareness of the static position of a joint. JPS has been tested on the human knee joint by means of an angle reproduction test. This task included the following sequences. The leg was moved passively, by means of a motor drive, from two different start positions (15 degrees and 75 degrees) to a certain target angle and, after a time of 8 s, it was returned to the start position; subjects had to reproduce the former target angle. Several target angles, mild flexion (30 degrees), intermediate flexion (45 degrees), and strong flexion (60 degrees), were used. Depending on the start position, the movements matching these targets were flexions or extensions. At least for the intermediate position different threshold values should be expected for flexions and extensions, if hysteresis has an impact. Moreover, the JPS measure should show a dependence on movement velocity and independence on distance. Of the variables tested, only movement direction but not movement velocity or distance had a statistically significant impact on the dependent constant angle error (difference between reproduction and target angle). The target angle of 30 degrees was exactly reproduced (-0.14 degrees), independently of the start position. The 45 degrees target angle was significantly underestimated (-4.39 degrees) when matching that position by flexions (starting at 15 degrees) compared to an overestimation (2.27 degrees) when matching that position by extensions (starting at 75 degrees). The target angle of 60 degrees has been constantly underestimated (-3.80 degrees), independently of the start position. Therefore, hysteresis, the dependency of the movement's direction, neglected in the past, should be considered in future tests of JPS or studies considering the role of movement parameters for motor control.

Proprioception in people with anterior cruciate ligament-deficient knees: comparison of symptomatic and asymptomatic patients

STUDY DESIGN

Nonrandomized prospective study.

OBJECTIVE

To evaluate proprioception in 2 groups of patients with anterior cruciate ligament (ACL) deficiency who had different severity of symptoms.

BACKGROUND

Defective proprioception has previously been found in patients with ACL-deficient knees. It has been suggested that sensory receptors of the ACL and other knee joint ligaments contribute to proprioception and knee joint function and stability.

METHODS AND MEASURES

A total of 17 patients with ACL deficiency (mean [SD] age, 28.8 +/- 5.6 years; range, 22-39 years) with few, if any, symptoms were compared with 20 patients with ACL deficiency (mean [SD] age, 26.6 +/- 6.1 years; range, 18-39 years) having instability and episodes of giving way. The groups were compared with each other and with an age-matched reference group of 19 nonimpaired subjects. Their mean (SD) age was 25.6 +/- 3.7 years (range, 20-37 years). Three tests of proprioception were used: threshold to detection of passive motion from 2 starting positions (20 degrees and 40 degrees of knee flexion) toward flexion and extension, active reproduction of a 30 degrees passive angle change, and visual reproduction of a 30 degrees passive angle change. The Wilcoxon rank sum test was used for between-group comparisons.

RESULTS

Symptomatic patients had higher threshold to detection of passive motion in their injured side in the flexion trial from 20 degrees (median of 1.5 degrees vs median of 0.5 degree) and in the extension trial from 40 degrees (median of 1.0 degree vs median of 0.5 degree) than the asymptomatic patients. No differences were found in the other threshold tests, active or visual reproduction tests.

CONCLUSIONS

Patients with severe symptoms related to ACL deficiency were found to have inferior proprioceptive ability in some measurements compared with patients with a good knee function. The findings indicate that proprioceptive deficits might influence the outcome of an ACL injury treated nonoperatively.

The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study

Stair climbing is a closed kinetic chain exercise that is thought to be useful for knee rehabilitation following anterior cruciate ligament (ACL) reconstruction while protecting the graft from excessive strain. The objectives of this study were to measure the strain produced in the anteromedial band (AMB) of the normal ACL during stair climbing in vivo. We have previously shown that the normal AMB strain pattern during knee passive flexion-extension motion is similar to that of an ACL graft immediately after graft fixation. We successfully tested five subjects with normal ACLs, who were candidates for arthroscopic meniscectomy under local anesthesia. AMB strain was measured in vivo using the Differential Variable Reluctance Transducer (MicroStrain, Burlington, VT). The stair climbing activities were performed on a StairMaster 4000PT (Randall Sports Medicine, Kirkland, WA). Two different climbing cadences were evaluated; 80 and 112 steps per minute. Consistent with our previous studies of ACL biomechanics, strain values increased as the knee was moved from a flexed to an extended position. The mean peak AMB strain values for the 80 and 112 steps per minute conditions were 2.69% (+/-2.89&) and 2.76% (+/-2.68%), respectively. These values were not significantly different. Compared with other rehabilitation activities previously tested in the same manner, the AMB strain values produced during stair climbing were highly variable across subjects. High strain values were observed in some patients but not in others.

A study of shoulder motions as a control source for adolescents with C4 level SCI

This study quantitatively examined and compared the shoulder motions of C4 level spinal cord injury (SCI), C5 level SCI, and able-bodied persons as a command source. The study was motivated by both the success of shoulder control in functional electrical stimulation (FES) systems designed for C5 level SCI people and the lack of quantitative information on the shoulder motion of persons with C4 level SCI. A dual-axis transducer was used to monitor the elevation/depression and protraction/retraction angles of each subject's shoulder while they performed three experimental sections which examined: the range of active shoulder motion; the ability to move incrementally to discrete positions with the aid of visual feedback; and the ability to hold discrete shoulder positions for an extended period without visual feedback. Results indicated that each group had the largest average shoulder displacements (abled = 23 degrees +/- 4 degrees, C5's = 14 degrees +/- 3 degrees, and C4's = 9 degrees +/- 3 degrees) while attempting to elevate and that on average the C4 group had the smallest range of active shoulder motion. No statistically significant differences between the groups were found in either the accuracy or stability of reaching discrete positions with the aid of visual feedback or in the accuracy of holding discrete shoulder positions for an extended period without visual feedback. The results suggest that within their limited range of motion the individuals with C4 level SCI retained shoulder control sufficient for use as an neuroprosthetic command interface.

Normal shoulder proprioception and the effect of lidocaine injection

The purpose of this study was to investigate the effect of age, dominance, joint position, and lidocaine injection on proprioception of the normal shoulder. Position sense and the detection of passive shoulder motion were investigated in 40 young (20 to 30 years) and old (50 to 70 years) subjects. An additional 20 young subjects were tested before and after a glenohumeral (n = 10) or a subacromial (n = 10) lidocaine injection was performed. A significant decline occurred in proprioception between the young and old age groups. No difference was observed between dominant and nondominant sides. Position sense was consistently less accurate in the maximum range of motion tested when compared with the lesser ranges tested for flexion and abduction. No differences were identified in the ability to detect motion in flexion, abduction, and external rotation in the younger group, whereas in the older group a difference was observed in flexion. No learning effect was detected for any test trial. No significant changes occurred in proprioceptive ability after either glenohumeral or subacromial lidocaine injection was performed.

Characterization of human joint proprioception by means of a threshold hunting paradigm

A method has been developed to measure the proprioceptive performance of movement detection in human joints, with the threshold hunting paradigm commonly used in other sensory modalities. Methods applied in former studies regarding movement detection were very time consuming (hours), making them not applicable to patients. Using the threshold hunting paradigm, the subject changes the parameter value continuously around the threshold producing a threshold hunting curve, which itself might be valuable for investigation of movement detection performance. The method presented here, is very quick compared to other studies in this field, especially when velocity is hunted and the threshold values are very low. The threshold parameter value is stable since there is a control at any time over the subject's stimulus perception. Furthermore, a Monte Carlo simulation showed that hunting curves can clearly be distinguished from guessing. Also reliability is given. All these points allow to use the method to evaluate the proprioceptive performance of a single individual. Considering the results, the method described may be useful for basic and clinical investigations regarding the proprioceptive performance limits of movement detection aspects.

The effect of intraarticular anesthesia and elastic bandage on elbow proprioception

Twenty uninjured male volunteers were studied to characterize normal elbow proprioception and to investigate the effect of applying an elastic bandage to the extremity and injection of an intraarticular anesthetic. A modified Biodex dynamometer was used to study position sense and detection of motion. In part 1 of the study position sense was tested by flexing the elbow to a predetermined angle, returning to the starting position, and then asking the subject to identify that angle. In part 2 detection of motion was tested by asking the subject to disengage the apparatus by pressing a stop button when movement was detected. The testing conditions in part 1 and part 2 were repeated after the elbow was wrapped with an elastic bandage and again after an intraarticular injection of 3 cc 1% lidocaine with the bandage removed. Ten additional subjects underwent testing of both elbows to examine the effect of arm dominance. Mean position sense was within 3.3 degrees+/-1.3 degrees of the actual angle in trials without an elastic bandage or an anesthetic. A significant improvement in position sense was observed (2.2 degrees+/-1.2 degrees) after an elastic bandage was applied (P < .004). No significant difference was seen in position sense after lidocaine was injected. The mean threshold for detection of motion in trials without an elastic bandage or an anesthetic was 4.21 degrees+/-1.56 degrees. No significant differences were seen in detection of motion observed with the elastic bandage or intraarticular anesthetic. No significant differences were seen between dominant and nondominant extremities for both position sense and detection of motion. The application of an elastic bandage improved position sense, suggesting that tactile cues from cutaneous or other extraarticular receptors may play a role in elbow proprioception. Intraarticular anesthesia, however, had little effect, suggesting that intracapsular receptors play a lesser role in elbow proprioception. The determination of proprioceptive qualities for the normal elbow can aid in the understanding of elbow function and provide a basis for defining its role in elbow dysfunction.

The strain behavior of the anterior cruciate ligament during bicycling. An in vivo study

Stationary bicycling is commonly prescribed after anterior cruciate ligament injury or reconstruction; however, the strains on the ligament or ligament graft during stationary bicycling remain unknown. In this study we measured ligament strain on eight patients who were candidates for arthroscopic meniscectomy under local anesthesia. Six different riding conditions were evaluated: three power levels (75, 125, and 175 W), each of which was performed at two cadences (60 and 90 rpm). The peak ligament strain values ranged from 1.2% for the 175-W, 90-rpm, condition to 2.1% for the 125-W, 60-rpm, condition. No significant differences were found in peak strain values due to changes in power level or cadence. Thus, the strain values were pooled across the six riding conditions tested. The mean peak strain value was 1.7%, a value that is relatively low compared with other rehabilitation activities previously tested. These data suggest that knee rehabilitation programs can be designed to include this selection of power and cadence levels without significantly changing ligament strain values. Thus, stationary bicycling is a rehabilitation exercise that permits the patient to increase muscle activity by increasing the power level or decreasing the cadence without subjecting the ligament or ligament graft to higher strain values.

Does ice immersion influence ankle joint position sense?

The purpose of this study was to determine whether a fifteen minute ice immersion treatment influenced the normal ankle joint position sense at 40% and 80% range of inversion and to establish the length of treatment effect through monitoring the rewarming process. Forty nine healthy volunteers between the ages of 17 and 28 were tested. Subjects were screened to exclude those with a history of ankle injuries. The subject's skin temperature over antero-lateral aspect of the ankle was measured using a thermocouple device during the fifteen minutes ice intervention and thirty minutes post-intervention. Testing of ankle joint position sense using the pedal goniometer was performed before and after a clinical application of ice immersion. The testing required the subject to actively reposition their ankle at 40% and 80% of their total range of inversion. The majority of subjects experienced numbness of the foot and ankle by the fifth or sixth minute during ice immersion. One minute after immersion skin temperatures averaged 15 degrees C + 1.7 degrees C. Skin temperature was seen to rise relatively rapidly for the first ten minutes and then slowed considerably. Subjects had not returned to the pre-test skin temperatures by thirty minutes. A significant difference in ankle joint position sense (p < 0.0499) following fifteen minutes of ice immersion was found. However, the magnitude of this difference (0.5 degree) would not be deemed significant in clinical practice. The research found no significant difference in joint position sense between 40% and 80% of the range of inversion both before and after cryotherapy. These findings suggest that the clinical application of cryotherapy is not deleterious to joint position sense and assuming normal joint integrity patients may resume exercise without increased risk of injury.

Comparison of Weight-Bearing and Non-Weight-Bearing Conditions on Knee Joint Reposition Sense

In this study, joint reposition sense of the knee in a non-weight-bearing (NWB) state and that in a weight-bearing (WB) state were compared, and it was determined whether a significant relationship existed between knee displacement (KD) and joint reposition sense. The dominant knees of 8 male and 12 female subjects (age 19–26 years, M ±SD= 21.5 ± 2.06) who had no previous history of knee dysfunction were tested for accuracy of angular reproduction in the WB and NWB states. There was a significant difference in the accuracy of angular repositioning between the two conditions, with the WB test having less deviation from the predetermined angle. There was a weak relationship between KD and the ability to reproduce specific angles of the knee. These results suggest that the WB or closed chain state of the knee was more accurate in the determination of joint position sense than the NWB or open chain condition.

The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension. A comparison of an open and a closed kinetic chain exercise

The effects of weightbearing (closed kinetic chain) and nonweightbearing (open kinetic chain) exercises on the biomechanical behavior of an injured anterior cruciate ligament or a healing anterior cruciate ligament graft are unknown. To understand the effects of these exercises on the healing graft, we measured the strain behavior of the normal anterior cruciate ligament in human subjects while they performed squatting, a closed kinetic chain exercise, and active flexion-extension of the leg, an open kinetic chain exercise. The maximum anterior cruciate ligament strain values obtained during squatting did not differ from those obtained during active flexion-extension. Also, anterior cruciate ligament strain values obtained during squatting were unaffected by the application of elastic resistance intended to increase muscle activity. These findings indicate that squatting, which produces a substantial compressive joint force, does not necessarily protect the anterior cruciate ligament more than active flexion-extension of the leg, which is characterized primarily by contraction of the dominant quadriceps muscle. These findings also demonstrate that increasing resistance during the squat exercise does not produce a significant increase in anterior cruciate ligament strain values, unlike increased resistance during active flexion-extension exercise.

The Effect of Ankle Bracing and Taping on Joint Position Sense in the Stable Ankle

The purpose of this study was to determine the proprioceptive effects of ankle bracing and taping. Proprioception was assessed in 26 subjects by evaluating ankle joint position sense, which was determined by the subjects' ability to actively reproduce a passively positioned joint angle. Testing was performed at positions of 30° of plantar flexion and 15° of inversion. Each subject underwent four trials at each test angle under three conditions: braced, taped, and control. For the plantar flexion test, both the braced condition and the taped condition significantly enhanced joint position sense when compared to the control condition. There was no significant difference between the braced and taped conditions. For the inversion test, the taped condition significantly enhanced joint position sense compared to the control condition. There was no significant difference between the braced and the control conditions or between the braced and the taped conditions. This study demonstrates that ankle bracing and taping improve joint position sense in the stable ankle.

Knee joint proprioception: a comparison between female intercollegiate gymnasts and controls

The role of proprioception as a protective mechanism has gained interest in recent years. From the clinical standpoint, several studies have dealt with ways to enhance proprioception following surgery and during rehabilitation. If kinesthesia (ability to detect passive motion) can be enhanced as a consequence of long-term athletic training, such training must be included as a part of the rehabilitation process to protect the patient from reinjury. Consequently, the purpose of this study was to compare the kinesthetic knee pattern between trained gymnasts and healthy nongymnasts. The proprioception testing device (PTD) was used to evaluate knee kinesthesia. From 45 degrees of flexion, the knee was passively extended with the PTD. The device was stopped by the subject when this passive motion was detected. Fifteen healthy college-age female gymnasts (mean age 19.3 years) and 30 normal volunteers (mean age 20.7 years) comprised our study sample. A one-way analysis of variance (ANOVA) was used to compare the mean values of the dominant gymnastic knee to the dominant knee in the control group. Results revealed statistically significant mean differences between the trained gymnastic group and the untrained control group (F1.34(.95) = 7.17, P = 0.011). The results of this study suggest that extensive training has a positive influence on knee kinesthesia in addition to increasing muscle tone. According to the findings of this and other studies, highly trained athletes possess enhanced neurosensory pathways which are speculated to develop as a result of long-term athletic training. Although definite conclusions cannot be made from our investigation, prospective studies can determine the true role of athletic training in proprioceptive patterns.

Effect of an ankle orthosis and ankle ligament anesthesia on ankle joint proprioception

The purposes of this study were to determine the effect of a rigid ankle orthosis (Aircast Air-Stirrup) and lateral ankle ligament anesthesia on ankle joint proprioception. Twelve noninjured subjects attempted to match nine reference ankle joint positions with their eyes closed before and after application of the ankle brace and before and after one or two of the lateral ankle ligaments (anterior talofibular and calcaneofibular) were anesthetized. Three-dimensional ankle joint orientations were recorded with a Motion Analysis system. No significant differences in the constant, variable, or absolute error were seen between subjects in the non-anesthetized and anesthetized conditions (P > 0.05), regardless of whether one or two ligaments were anesthetized. Thus, it appears that ligament mechanoreceptors contributed little to ankle joint proprioception, and that the afferent feedback from skin, muscle, and other joint receptors was adequate for the positioning task of the present study. Both the variable and absolute error in matching the reference positions were significantly less with the orthosis than without (P < 0.05). Application of an orthosis may increase the afferent feedback from cutaneous receptors in the foot and shank, which may in turn lead to an improved ankle joint position sense.

Diagnostic and operative arthroscopy of the knee under local anesthesia with parenteral medication

Arthroscopy of the knee under local anesthesia was performed on 102 patients for operative and diagnostic purposes between January and December of 1985. The procedures were performed on a same day basis without a pneumatic tourniquet. The operative record of each patient was reviewed to determine postoperative diagnosis and treatment. The data was matched to a patient questionnaire that measured individual reaction to local anesthesia. The effectiveness and level of patient acceptance of this anesthetic technique for operative arthroscopy was then evaluated. Ninety-one patients responded to the questionnaire, 82 of whom had prior anesthetic experience. Ninety-five percent of the patients had minimal or no discomfort during the procedure. Eighty percent indicated a preference for local anesthesia in the event of subsequent arthroscopy. No complications relating to the anesthetic agent were noted. Arthroscopy of the knee under local anesthesia for routine operative arthroscopy was found to be safe, reliable, practical, and to have a high patient acceptance rate.

Proprioception in the anterior cruciate deficient knee

Proprioception was quantified in a group of patients who had documented complete ACL tears. Threshold to detection of passive change in position of the knee was measured using a well-described test. Eleven patients with arthroscopically proven complete ACL tears and findings consistent with moderate to severe anterolateral rotatory instability were tested. Testing was done within the 30 degrees to 40 degrees range of knee flexion. Patients were blindfolded and the injured and uninjured knees were tested in random sequence so that the normal knee could serve as an internal control. Testing was also done in a blind manner, i.e., the examiner did not know which knee had been injured. An age-matched control group underwent identical testing. Potentially significant variables such as age, time from injury, and degree of rehabilitation as measured by thigh circumference and isokinetic testing of the knee were included in a multivariate analysis. Control subjects demonstrated virtually identical threshold values between their two knees, the mean variation being less than 2%. The test group, however, showed a significantly higher mean threshold value for the injured versus the noninjured knee (P less than 0.01), the mean variation being over 25%. Multivariate analysis demonstrated that changes recorded in the proprioception of the injured knee were attributable to the loss of the ACL rather than to other variables. Patients who have complete ACL tears and moderate to severe rotatory instability may also experience a decline in proprioceptive function of their knee.